The disclosures of Japanese Patent Application Nos. HEI 11- 143209 filed on May 24, 1999, and HEI 11-259467 filed on Sep. 13, 1999 including the specifications, drawings, and abstracts are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates to a start control apparatus for an internal combustion engine and a fuel nature determination apparatus. In particular, this invention relates to a start control apparatus for an internal combustion engine capable of performing a plurality of start controls when starting an internal combustion engine and to a fuel nature determination apparatus for determining the nature of fuel supplied to an internal combustion engine.
2. Description of the Related Art
As is described in Toyota Technical Review (Publication No. 4139 (Date of Publication Mar. 29, 1991)), for example, an apparatus for correcting a fuel injection amount in accordance with the nature of fuel supplied to an internal combustion engine is known. Fuel supplied to an internal combustion engine may be fuel containing a large amount of low volatility components (referred to below as heavy fuel) or fuel containing a large amount of high volatility components referred to below as light fuel). In comparison with light fuel, heavy fuel is unlikely to vaporize. Therefore, when heavy fuel is used, the concern exists that stable operation of the internal combustion engine will not be achieved. In the apparatus of the above related art, the time from when the internal combustion engine is started (for example, from when a starter switch is turned on by an operator) until the internal combustion engine actually begins to run (start time) is detected. Then, on the basis of this start time, a determination is made as to whether or not the fuel is of a heavy nature. The amount of fuel injected into the internal combustion engine is then corrected in accordance with the determined nature of the fuel. Accordingly, stable operation of an internal combustion engine can be guaranteed regardless of the nature of the fuel.
As described above, in the above apparatus, the nature of the fuel is determined based on the start time. Namely, the nature of the fuel is not determined if the internal combustion engine is not running. Accordingly, if an attempt is made to start an internal combustion engine using normal start control when the fuel is of a heavy nature, a considerable length of time passes before the engine is running and the concern arises that superior starting is difficult to guarantee.
The present invention was achieved in view of the above points. It is an object of the present invention to provide a start control apparatus for an internal combustion engine capable of ensuring superior starting regardless of the nature of the fuel. It is a further object of the present invention to provide a fuel nature determination apparatus capable of suitably determining the nature of fuel in the apparatus.
In order to achieve the first object above, the starting operation control apparatus for an internal combustion engine of the present invention includes a controller that capably selects and executes a starting operation from at least a first and second starting operation in accordance with a nature of fuel supplied to an internal combustion engine and a sensor that detects a running state of the internal combustion engine. When the sensor does not detect that the internal combustion engine is running within a predetermined time after starting of an internal combustion engine is begun using the first starting operation, the controller switches the starting operation to the second starting operation.
In this case, for example, when the fuel exhibits high volatility (light fuel), the controller selects the first starting operation and when the fuel exhibits low volatility (heavy fuel), the controller selects the second starting operation.
According to the above aspect, if there is no operation within a predetermined time when the internal combustion engine is started using the first start control which corresponds to light fuel, then it is possible to determine that it will take some time for the starting operation of the internal combustion engine to be completed (i.e., it will take some time until the engine is running) because the fuel is of a heavy nature. In this case, by switching the start control from the first start control to the second start control which corresponds to heavy fuel, it is possible to ensure that the internal combustion engine will be started even if the fuel is of a heavy nature.
In order to achieve the second object of the present invention, the fuel nature determination apparatus for determining the nature of fuel supplied to an internal combustion engine of the present invention further includes a torque controller that limits the output torque of an internal combustion engine after the internal combustion engine is running, and a fuel nature determining apparatus for determining the nature of fuel based on parameters which correspond with the output torque after the internal combustion engine is running and a predetermined threshold value. Further, the fuel nature determining apparatus alters the threshold value when the torque controller limits the output torque.
When the output torque is limited, the concern exists that the determination of the nature of the fuel determined on the basis of parameters which correspond to the output torque may be in error. According to the above aspect, when the output torque is limited, a threshold value for determining the fuel nature is altered. Consequently, even if the parameters vary due to the torque limitation, the possibility of mis-determination of the fuel nature may be minimized.